某公司投资购买设备有A、B、C、D四个方案可以选择：其寿命周期费用分别为300万元、300万元、285万元、275万元，系统效率分别为375吨／日、330吨／日、350吨／日、330吨／日。该公司每日350吨材料即可满足所有需要，通过费用效率分析后得出最佳方案是（）。

A.方案A

B.方案B

C.方案C

D.方案D

Scientists have developed a non-stick chewing gum(口香糖). The new gum can   小题1: (remove) easily from pavements, shoes and clothes. It’s the result of polymer (聚合体) research at the University of Bristol and could be launched commercially in 2008.   小题2:  it catches on(流行), the product will solve  小题3:  major headache for present authorities around the world.

“A great 小题4:  (disadvantage) of our Clean Gum is that it is easy to remove and has the potential to be 小题5: (environment) degradable (可降解的),” said Terence Cosgrove, a professor of chemistry  小题6:  helped to found a company called Revolymer to commercialize the technology.

Today’s chewing gums are made  小题7:synthetic latex(人工制造的乳液), which is resistant to the weather and is strongly sticky. The new gum adds a special polymer to change its properties(特性),    小题8:  (make) it far less sticky.

In two street trials,   小题9:  commercial gums remained stuck to the pavement   小题10:    Clean Gum came away naturally in all cases.